Abstract: We propose to genetically reprogram cells in vivo to induce new tissue development in post-embryonic vertebrate animals. Our ultimate goal is to grow replacement organs in an adult vertebrate animal using genetic reprogramming. The ability to grow replacement tissues will be critical for treating and curing diseases such as diabetes, liver disease, and heart diseas and for repairing/replacing damaged or lost organs and limbs sustained from traumatic injury. Our primary strategy is test for the efficacy of different combinations of factors implicated in th process of development, regeneration, and of making iPSCs (induced pluripotent stem cells) to induce new tissue development in post-embryonic animals. Our research proposal will focus on growing ectopic pancreas and liver tissues in the foregut endoderm, and ectopic ss-cells in different various places in the body. Currently, the most popular approach to engineering potential therapeutic cells or tissues is primarily via an in vitro strategy: through directed differentiation of embryonic stem cells (ESCs) or from iPSCs. However, there are several potential fundamental obstacles with this approach. Cultured cells may acquire extensive deleterious genetic and epigenetic changes (oncogenic or immunogenic mutations) that would normally be rejected and eradicated from the body, but would continue to thrive in culture. Also, although much progress has been made in differentiating various cell types in the dish, it remains challenging to grow whole organs in 3D. Further, it is still unclear how tissues cultured in a dish such as cardiomyocytes derived stem cells would integrate and become a functional part of the host heart following transplantation. Therefore, many complications have arisen with in vitro approaches to generating therapeutic cells and organs. Much less emphasis has been invested in generating new tissues in vivo, which may circumvent these obstacles. We propose to apply our unique insight on liver and pancreas progenitor biology and combine it with our new technology to precisely induce transgene expression to reprogram endoderm cells to grow ectopic pancreas, liver, and ss-cells. Many fundamental questions regarding the feasibility and effectiveness of in vivo cell reprogramming is largely unexplored. Our studies will allow us to evaluate these issues: Is it possible to grow whole new organs in an adult animal? How amendable are different somatic cells (particularly in the gut endoderm for this proposal) to in vivo genetic reprogramming? Are certain adult cells, maybe progenitors, more poised for genetic reprogramming? Will induced organs integrate effectively to adjacent tissues and be functional? Are they less likely to accumulate mutations or be rejected by the immune system? Will cancer risks increase with our genetic manipulations? Can expression of iPSC induction genes make most somatic cells in vivo more reprogrammable? Our proposed work will allow us to begin to ask these fundamental questions. Public Health Relevance: We propose to genetically reprogram cells in vivo to induce new tissue development in post-embryonic vertebrate animals. Our ultimate goal is to grow replacement organs in an adult vertebrate animal using genetic reprogramming. The ability to grow replacement tissues will be critical for treating and curing diseases such as diabetes, liver disease, and heart disease and for repairing/replacing damaged or lost organs and limbs sustained from traumatic injury.